docs: def _get_distance_term(self, C, rjb, mag):
          """
          Returns the general distance scaling term - equation 2
          """
          c_3 = self._get_anelastic_coeff(C)
          rval = np.sqrt(rjb ** 2. + C["h"] ** 2.)
          return (C["c1"] + C["c2"] * (mag - self.CONSTS["Mref"])) *\
              np.log(rval / self.CONSTS["Rref"]) +\
              c_3 * (rval - self.CONSTS["Rref"])